A fundamental role for NO-PLC signaling pathway in mediating intracellular Ca 2+ oscillation in pancreatic acini

Abstract

The aim of the present study was to investigate the possible interaction between intracellular Ca 2+ and nitric oxide (NO) in rat pancreatic acinar cells, especially intracellular signaling events. (1) Nitric oxide donors SNP (0.1–100 μM) and NOR-3 (50–400 μM) induced Ca 2+ oscillations in fluo-4-loaded acini, that appeared to be analogous to what we usually observe in acini stimulated with physiological secretagogues such as CCK-8 and this oscillations were abolished in the presence of carboxy-PTIO. (2) The NO donors-evoked Ca 2+ oscillations were not abolished even in the absence of extracellular Ca 2+ but totally disappeared when cells were pretreated with thapsigargin, a sarcoplasmic-endoplasmic reticulum Ca 2+ ATPase (SERCA) inhibitor. (3) Inhibition of guanylate cyclase with 1 H-[1,2,4] oxadiazolo [4,3-a] quinoxaline-1-one (ODQ) attenuated Ca 2+ oscillations evoked by SNP in the absence of extracellular Ca 2+. (4) Inhibitors of phospholipase C activity, U73122 and the IP 3R blocker xestospongin C, both abolished the SNP-induced Ca 2+ response. (5) Furthermore, we found that both CCK-8 and carbachol (CCh) induced NO production in DAF-2-loaded acinar cells and that an inhibitor of NO synthase, N G-monomethyl- l-arginine (L-NMMA), significantly reduced CCK-8-induced Ca 2+ oscillation. These results indicate that NO mobilizes Ca 2+ from internal stores through activation of guanylate cyclase and resultant cGMP production. In addition, PLC activation of IP 3 production is also suggested to be involved in Ca 2+ mobilization via IP 3 receptors. This suggests the presence of cross-talk between Ca 2+ and NO in pancreatic acini and this cascade may, at least partially, participate in physiological secretagogue-evoked Ca 2+ dynamics in pancreatic acinar cells.